CARAIB: A GLOBAL MECHANISTIC VEGETATION MODEL TO STUDY THE CO2 EXCHANGE BETWEEN THE ATMOSPHERE AND THE CONTINENTAL BIOSPHERE

The TM2 atmospheric transport model, a parameterization of soil heterotrophic respiration and a mechanistic model of carbon assimilation in the biosphere (CARAIB) are combined to estimate the net primary productivity of the continental vegetation. The model includes the determination of the leaf area index (LAI) of the various vegetation covers, the CO2 assimilation by the leaves, and the respiration of standing biomass. It also includes a soil hydrological model forced with monthly mean air temperature, precipitation and solar radiation fields and using a stochastic generation of daily weather within each month. It is shown that the seasonal fluctuations observed at various monitoring stations can be well reproduced, thus validating the mechanistic approach adopted to calculate the global net primary productivity. A Fourier analysis of the modelled atmospheric signal is performed to quantify the relative importance of the vegetation in the different latitude zones and the contribution of the various vegetation types. In the southern hemisphere, the calculated phase and amplitude of the CO2 signal are not so well reproduced since atmosphere-ocean exchanges should also be considered in addition to the biospheric source. The latest updates and simulations performed with the model will be presented and discussed